It's clear then: the rule for d0 will remain unclear. It doesn't matter anyway, because no rule calls for d0 and no sane person will ever use on for fear of inducing the rule of unclarity.

However, I continue to argue in favour of my first argument. I deem that if a d0 is rolled and the result is 0, a roll of d6 is called for because it is a critical success. The rule clearly states that when the highest number is rolled on a die, it is declared a critical success. And 0 is the highest of 0, eh?

Often, literally, a pillow fight but may include similar situations like volleyball, particularly when wardrobe is skimpy and the action is bouncy.

I'd like to add the fascinating side note that, since a Critical Failure only occurs when all dice come up specifically as "1," it means that any roll involving at least one d0 can never be a true Critical Failure.